Genealogy - 1 Nephi 6

Nephi says that it is enough to know that he is a descendant of joseph. But he also mentions that his purpose is to bring people to the god of abraham isaac and Jacob who are also his ancestors. Why was it important to him to know his ancestors and are his reasons different than mine? Covenants made with fathers is an important reason. Are there other reasons? In chapter 5 we do learn that there was a responsibility to keep the records which ran in family from joseph of old to Laban.